It is frequently desirable to accurately monitor a patient's weight during the course of a hospital stay. This requires frequent weighing of the patient. However, it is often impractical, if not impossible, to remove patients from a hospital bed to weigh them, particularly on a regular or frequent basis. In order to overcome this difficulty, systems have been designed to weigh patients while they remain in the hospital bed. An example of one such system is shown in U.S. Pat. No. 4,926,951 to Carruth et al. However, difficulties have been experienced with the accuracy, repeatability and long-term reliability of existing systems.
This is due to a variety of reasons, including the many possible positions of the patient on the bed, and the inability of such systems to combine sufficient sensitivity to produce good weighing results and sufficient durability to withstand the high forces typically present on various portions of the bed during normal use thereof. For instance, the weighing systems of such beds are subject to large twisting forces, due to complex bed construction and the effect of certain bed positions, such as the Trendellenberg position. These forces will vary in magnitude, depending upon the particular positional configuration of the bed and the position of the patient on the bed. In addition, movement of the bed from place to place, and frequent change in bed positional configuration (from one configuration to another) tend to compound the difficulty of maintaining high accuracy for a weighing system on such beds.
All of the above reasons combine to make accurate weighing of patients in a hospital bed a difficult engineering and design problem.